Dynamic concepts in neutron polarization

A new method of polarizing a neutron beam is proposed, which in contrast to conventional polarizers allows to make use of 100% of the incident intensity. It exploits the fact, that neutrons of different spin states differ in velocity after they have passed through an arrangement of crossed static and time-dependent magnetic fields. Provided the neutrons initially being sufficiently monochromatic, the two spin states can be separated in momentum space and be forced to point into the same spatial direction by means of a momentum-dependent spin rotation procedure. With presently available magnetic field technology (or nuclear pseudomagnetism) this dynamic method is applicable at continuous sources to polarize highly monochromatic thermal neutrons as those obtained by perfect crystal diffraction. The method seems to be particularly powerful, however, in the production of polarized cold and ultra-cold neutrons, where energy spreads of 1% and more are admissible. It is shown that at pulsed sources even polychromatic neutrons can be polarized with this technique.